This proposal is for competing renewal application of R01 DK56884 supported for 4 years. Bioactive polymers have been designed and tested for improved oxygen transport to the encapsulated islets by hemoglobin crosslinked with poly(ethylene glycol) (Hb-C) and for islet stimulation by water-soluble polymer conjugates of sulfonylurea (SU) and glucagon-like peptide-1 (GLP-1). The experimental results demonstrated that the polymers are effective in promoting the functioning and prolonging the life-span of encapsulated islets. In this proposal, the stabilization and expansion of the functionality of the bioactive polymers derived from Hb and GLP-1 intended for a longer duration will be pursued. Tetrameric Hb is prone to oxidation (metHb production), dissociation and denaturation. GLP-1 is also subject to destabilization and denaturation in physiological environment. The central research theme in this aspect will be placed on the stabilization of Hb and GLP-1 based bioactive polymers. For Hb-C, by using intramolecularly crosslinked and/or pyridoxalated Hb and introducing antioxidant enzymes to Hb-C, the stability of Hb-C could be promoted. In addition, the oxygen binding property will be optimized for improved oxygen supply to islets with a detailed mechanistic study of facilitated oxygen transport by directly measuring the profile of oxygen partial _ressure and Hb-C diffusivity in islet capsules. For GLP-1 conjugate, zinc-induced crystallization or precipitation approach will be employed. The precipitate will then be allowed to equilibrate with bioactive soluble GLP-1 conjugates and will be the source of continuous supply of GLP-1 conjugate in islet capsules. A new subject in this research is centered on the construction of effective polymeric gene carriers to pancreatic islets for the transfer of anti-apoptotic Bcl-2 gene. The protection of encapsulated islets from early cytokine assault when transplanted by Bcl-2 expression is an additional critical factor for determining islet survival. This challenge relies on our observation that SU-conjugate was actively internalized into the cells (islets and insulinoma cell line) that express SU receptors. Because the bioactive polymers designed were based on different mechanisms for the same goals of improved islet functionality and prolonged life-span, the combined effects of the bioactive polymers will be evaluated to verify if there is synergistic, summing up or one-component dominant effect.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
2R01DK056884-05A1
Application #
6820034
Study Section
Surgery and Bioengineering Study Section (SB)
Program Officer
Appel, Michael C
Project Start
2000-03-01
Project End
2008-05-31
Budget Start
2004-06-01
Budget End
2005-05-31
Support Year
5
Fiscal Year
2004
Total Cost
$224,250
Indirect Cost
Name
University of Utah
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
009095365
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Nadithe, Venkatareddy; Mishra, Deepa; Bae, You Han (2012) Poly(ethylene glycol) cross-linked hemoglobin with antioxidant enzymes protects pancreatic islets from hypoxic and free radical stress and extends islet functionality. Biotechnol Bioeng 109:2392-401
Nadithe, Venkatareddy; Bae, You Han (2011) Hemoglobin conjugates with antioxidant enzymes (hemoglobin-superoxide dismutase-catalase) via poly(ethylene glycol) crosslinker for protection of pancreatic beta RINm5F cells in hypoxia. Tissue Eng Part A 17:2453-62
Nadithe, Venkatareddy; Bae, You Han (2010) Synthesis and characterization of hemoglobin conjugates with antioxidant enzymes via poly(ethylene glycol) cross-linker (Hb-SOD-CAT) for protection from free radical stress. Int J Biol Macromol 47:603-13
Kang, Han Chang; Bae, You Han (2009) Transfection of insulin-secreting cell line and rat islets by functional polymeric gene vector. Biomaterials 30:2837-45
Kang, Han Chang; Bae, You Han (2009) Transfection of rat pancreatic islet tissue by polymeric gene vectors. Diabetes Technol Ther 11:443-9
Kang, Han Chang; Bae, You Han (2006) Polymeric gene transfection on insulin-secreting cells: sulfonylurea receptor-mediation and transfection medium effect. Pharm Res 23:1797-808
Kim, Sungwon; Wan Kim, Sung; Bae, You Han (2005) Synthesis, bioactivity and specificity of glucagon-like peptide-1 (7-37)/polymer conjugate to isolated rat islets. Biomaterials 26:3597-606
Kim, Yong Yeon; Chae, Su Young; Kim, Sungwon et al. (2005) Improved phenotype of rat islets in a macrocapsule by co-encapsulation with cross-linked Hb. J Biomater Sci Polym Ed 16:1521-35
Kang, Han Chang; Kim, Sungwon; Lee, Minhyung et al. (2005) Polymeric gene carrier for insulin secreting cells: poly(L-lysine)-g-sulfonylurea for receptor mediated transfection. J Control Release 105:164-76
Kang, Han Chang; Lee, Minhyung; Bae, You Han (2005) Polymeric gene carriers. Crit Rev Eukaryot Gene Expr 15:317-42

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